API versioning contract is inconsistent: version edge cases not exercised across controllers

[nanaf6203-bit]

Context

DEFAULT_API_VERSION = v2, v1 is deprecated with sunsetDate 2026-12-31, v2 released 2026-04. Controllers mostly have no per-version DTO differences, and no endpoints intentionally diverge (v1 vs v2) apart from the versioning module's own examples.

Problem

Deprecation of v1 is implied but no real v1 responses are frozen; consumers get v2-shaped payloads from a 'v1' that was never pinned, making the sunset date aspirational. Without per-version fixtures, backward-compatibility.service has little to protect.

Proposed approach

Inventory endpoints and choose a versioning policy (URI vs header) to document in docs/API_VERSIONING.md; freeze v1 response examples (Swagger examples/snapshot tests) and add drift detection for v1 vs v2.

Acceptance criteria

• v1 output for key endpoints is snapshot-pinned and CI detects drift.

[Mitch5000]

@Mitch5000 has applied to work on this issue as part of the Stellar Wave Program's 9th wave.

please maintainer... Can i have this?

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[Lakes41]

@Lakes41 has applied to work on this issue as part of the Stellar Wave Program's 9th wave.

Boss man, better gimme that thing

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[drips-wave]

Congratulations, @Lakes41! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on September 30, 2026.

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